Credit:
Brian Richmond / George Washington UniversityThe George Washington
University professor Brian Richmond and his colleagues have
discovered a set of 1.5 million-year-old human ancestor
footprints in Kenya that show the earliest direct evidence of a
modern human style of upright walking called bipedalism. The
discovery of ancient hominin footprints is an incredibly rare
event, and the new prints are the second oldest in the world
after the 3.7-million year-old prints in Laetoli, Tanzania,
making this one of the most important discoveries in recent years
regarding the evolution of human walking. For the first time
ever, research establishes a methodology for three-dimensional
analysis and comparison of ancient human footprints.

Matthew Bennett, Bournemouth
University professor and lead of the study, said, “Our
findings from Ileret show that by 1.5 million years ago, hominins
had evolved an essentially modern human foot function and a style
of bipedal locomotion that we would recognize today.”

In a project led jointly by
Jack Harris, Rutgers University professor; David Braun,
University of Cape Town; and the National Museums of Kenya, the
research team excavated two distinct sedimentary layers in a
single outcrop at Ileret, Kenya, to reveal footprints preserved
in fine-grained mud. These surfaces have been dated precisely
through interbedded volcanic ash layers to 1.51 to 1.53 million
years old and were digitally scanned by Bennett to create
three-dimensional digital elevation models of the prints, which
are accurate to a fraction of a millimeter.

The international team from the
United Kingdom, United States, South Africa, and Kenya found that
the prints were probably formed by the species Homo erectus. The
unique structure of the modern foot is characterized by an
adducted big toe that is in line with the other toes, large and
robust heel and ankle bones, and a pronounced longitudinal arch
and short toes—all of which are evident in the fossil
footprints.

By applying geometric
morphometric statistics to biological landmarks placed on the
footprint scans, the team was able to determine that the shapes
of these prints significantly are more like those formed by
modern humans compared to the prints from Laetoli, Tanzania,
which are dated to 3.75 million years and believe to have been
formed by Australopithecus afarensis.

Based on the size and the
stride pattern of these newly discovered footprints, the team
determined that the individuals responsible would have been
approximately 1.75 meters (about 5'9") in height.

“The size and stature
estimates derived from the Ileret prints compare well with those
of our distant ancestor, Homo erectus, and are too large to have
been formed by other hominin species living in this part of
Africa in the early Pleistocene,” said Richmond.

Harris said, “These
footprints, together with evidence from the archaeological
record, support the hypothesis of a hominin with a larger home
range and enhanced dietary quality, giving us an emerging picture
of the paleo-biology of early Homo erectus that suggests a shift
in cultural and biological adaptations relative to earlier
hominins.”

The process of laser scanning
footprints not only provides a unique method of analysis but also
allows for their preservation. The area within which these prints
are located is steadily eroding, thereby placing this valuable
site at great risk. The digital scans are easily replicable and
can be transformed into real-life casts available for museum
display around the world or even in the classroom. The National
Museums of Kenya has pioneered research in early hominin
evolution in Northern Kenya over the last 40 years.

“These footprints are one
of the most important discoveries of recent years, and the museum
is doing everything possible to ensure the safety of this unique
site,” said Emma Mbua of the National Musuems of Kenya. “We
hope to bring this discovery to worldwide audiences in the
future.”

The article, “Early
Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints
from Ileret, Kenya” appears in the Feb. 27 edition of
Science. Science is a weekly, peer-reviewed journal that
publishes significant original scientific research, plus reviews
and analyses of current research and science policy.